7 & 7 Synch and 7-day progesterone- based protocols for estrus synchronization prior fixedtime artificial insemination in multiparous beef sucked cows

Abstract

Estrogen-based protocols combined with a progestinreleasing intravaginal device (P4RID) and prostaglandin (PG) synchronize follicle wave emergence prior to artificial insemination (AI) in Bos taurus, with pregnancies per AI (P/AI) ranging from 40 to 60%. Gonadotropin-releasing hormone (GnRH) based protocols + P4RID + PG rely on the presence of a physiologically mature dominant follicle at initial GnRH. Failure to induce ovulation represents a major obstacle to improve P/AI. Pre-synchronization by PG + P4RID 7 days in advance of GnRH increase likelihood of ovulation following GnRH. The aim of this trial was to evaluate fertility in suckled beef cows using GnRH or estrogen treatments with or without pre-synchronization